Laserjet M551 won't print color

[Eredifer]

I recently bought a Laserjet M551 that had been bought at a liquidation auction.  It appears to have very little use and has brand new cartridges in it. 

No matter what I try it doesn't want to print in color.  I've performed a cold reset.  I've swapped out the controller board for one I bought on Ebay.  It gives no error codes.  I've tested the sensors and the color motors - all check out fine. 

It prints perfectly in black and white - fast and perfect registration. 

Is there some kind of hardwire switch that turns the color off?

[davidzuts]

Go to the admin menu on the printer and then go to troubleshooting and see if there is a menu option for pq troubleshooting which should print a mess of pages from the menu on the printer. See if you get color. I think you will. On these printer the config and info pages all print in black and white so you need to try other pages to see if the color issue is with the printer or the driver. My gut tells me it is with the driver.

http://www.hp.com/cpso-support-new/pq/M551/

If the test indicates a driver issue see the link below to solve.

http://h20564.www2.hp.com/hpsc/doc/public/display?docId=emr_na-c02005997

[Eredifer]

Thanks for the reply, but no, it's definitely not printing color. 

When I print the color alignment charts from the printer control panel - black prints perfect - the other colors don't print.  When I print the Demo page from the printer control panel, only the black and white portions print - the HP logo should print blue, no blue.  

I changed out the DC controller board; I upgraded the firmware; I did a cold reset on the machine. 

I've read through nearly the entire service manual and I can't find anything that talks about no color at all.  I've found sectons on color smearing, and one color missing, and toner not feeding.  In this case something is keeping it from turning on all the colors.  I also checked the alienation motor and can see it moving the cams on the color drums.   I checked the sensors and they are fine.  It's not throwing any trouble codes at all.  That's why I thought there has to be a switch somewhere.   

[davidzuts]

Perform the engine test per the attached instructions. If you get colored lines on the page, the the formatter is probably the issue. If still no color the issue is probably the high voltage ps or the laser/scanner assembly.

[Eredifer]

I have performed the engine test both before and after I changed the controller board - black only.

If either the high voltage supply or the laser scanner were bad, then I think it would affect black as well since the blue and black both share a laser/scanner and all colors share the high voltage power supply. 

There is something shutting off all the colors. 

I can tell the disengagement motor M10 is working, because I can see the cams that engage and disengage the colors move, however I cannot tell whether they are positioned correctly and I can't find anywhere that there is a sensor that detects whether it positions correctly.  The only thing I can think is that they are misaligning somehow.

[Eredifer]

I appreciate everyone's help so far.  Any other ideas? 

I think I'm going to dig into it and remove the disengagement motor for the color cams and see if there is a gear stripped or something.   I do hear sort of a popping noise when I run the test on that system.   I can't tell if that noise is just the normal switches moving or something wrong with the drive system.

I've never worked on a printer before, so I don't really know what I'm doing, however I have an ability to fix almost anything mechanical.  I struggle a little bit on the electrical end sometimes.